Method of stripping photographic emulsions



Vlconjunction with therear flm (B)` ofabipack Patented Sept. 2, 1952 STRIPPING PHOTOGRAPHIC YriuULsIoNs i Jacob Quentin Umberger, Holmdel, and Arthur William Grumbine, Parlin, vN. J., assignors to'v E. I. du Pontrde- Nemours & Company, Wilmington, Del., a`c orporation of Delaware-A No Drawing'. Application May-17, 1948,

Serial No. 27,607

i 12I claims. (01.' 95-2) METHOD "F This invention relates to photography and' more particularly to a process for insolubil-izing stripping layers in photographic lms. vStill morerpar- -tcularly it. relates to la process ior-vtransferrmg lan image-bearing Alayer from a stripping hlm to v another support which involves insolubilization and resolubilization of the stripping layer. l

Photographic stripping lms are described in ccpending Jennings application Serial N o, 651,996 led March 5, 1946 now U. S. Patent No.2,462,503. The strippingnlms of that application constitute the front lm (A) of a bipack. The stripping layer whichis disposed between two gelatine silver halide Vemulsion layers is composed essentially of aV .water-soluble macromolecular acetal of -a hydroxyl polymer containing a pluralityof recurring intralinear I CH2-orion l i orvinyl alcohol units. These acetalsl are Water:- soluble lby Virtue of the fact that the hydrocarbon nucleus ywhich isglinkedto the hydroxylpolymer nucleus through "an acetal linkage has a hydrolgenatom' substituted bya grouptakenfrom the class consisting of COOZV and SOsZgroups wlrere- Z is a hydrogen atom or a waterg-soluble-cation,. e.` g., alkali imetal, ammonium ,or anamine salt group; 'f f` Aff.- A T The stripping-films just described are used-'in which. consists of a transparent lm base *carry- -ingai light-.sensitive gelatine silverffhalide emul- `sion layer.A Thiszlayer'is generallyv sensitive to 'green or red light." In'using'the bipackiilm-the respective emulsion surfaces of the iront film l(A) and .the rear film (B) are placedpin kcontactan'd disposed lin a camera so that the front lmzis first exposed through the base. The two-lmssare then developed whereby three-color separation records are formedin therespectiveflight-sensitive emulsion layers of theloip-ack` ele1ne`nt The color separation-records of Vvthe'front (A), in

` one ...practical use' lare fldevelopedg "jX'ed and washed, and rolled intol contact with thegelatin the gelatin-blank film istl'en strippedfgfromrthe -.lower image-bearing layer. The gelatin-blank lmshould, of course, bet.placedjinregistration film can then be superimposedin register on a "ftransparent support.` whereby 'a positive A'multiy'color picture lisfformed for Jthe Iseparation recorvzs'u method for insolubilizing the water-soluble s ipf It has been found that stripping venient to. conduct a stripping operation *Y .same areaas the continuous developingmac Y A invention.

.extended washingin water.r -zagehts apparently form "ai complex v'vvil'shxthe can be used for printing-purposes. The stripping films of theaforementioned applicatiomwhile commercially feasible have the disadvant L hat the stripping layers dissolve or-loosendurin the washing stepy after development .and rxatio'n. Hence, thestripping action should be .carried dut immediately after the photographic processing has been completed. This sometimes, 'isdsfadvantageous since it is often desirable tol'strip continuous links of motion picture iilm at arate different from that at which the-,nlm vvpasses through the continuous developing."and`` machine, Furthermore, `it is sometime An object of this invention is to pro ping layer of a stripping lm. Another objelis to provide a method forinsolubilizing such ,a llayer and later r'esoluloilizingV itso thatV stripping can be accomplished. A further object is toprovide a simple and economical vmethod for delaying the stripping action -ofa Water-soluble polyvinylV acetal stripping layer, Still other objects l.will be apparentfrom the following descriptionio t layers .ms

of the type referred to and disclosed above canine iinsolubilizedby treating them with amaqueous vsolution containing; a water-soluble inorganic polyvalent metalv` gelatin-hardening .agent nwhich yields metalcations in solution having Hrfl/alence of 3 to 4, including theA salts'of aluminum, chromium, iron, thorium, zirconium, titaniumcerium and vanadium, e. g the chlorides, bromideaggaoetates,-1sulfates and mixedsalts such as po tassiurn aluminumV sulfate, iron ammonium sulfate, befQre or after development-,or xation, but priortoany The hardening water-soluble macromolecular polyvinyl acetal sulfonic or carboxylicacid `compounds and insoll ubilia'ev the same. Theacetals arepolyelectrolytes bearing layer. of ,'the'frontlm. heing'fadherent .to

I v-#during thelnormal washing steps.

Asolution-fprior .to` making thelayerfo element is maden *It .is A.preferably .f Carr of: the anionicftype and possiblyrzform apolyvalent or .complexsalt with the;V metalmfthe 1 hardening agent.- However, regardles's-lofthe-the- ,oretical explanation, the'layervbecomes, insoluble 'v andino 'dissolving onloosening ofthe layer occurs The insolubilizationy can be accomplished by I during the t.processing of1 theielementto crm-Sia visible image and after exposure..v EvThe'-fc'li'igi'nal the Y stitutes the front'lm (A) of a bipack. slit and perforated to form a mot-ion picture lm.

light-sensitive layers thus are preferably imagebearing, that is, they contain a latent image or a developed image before the stripping layer is insolubilized. The insolubilization treatment is preferably carried out during or after fixing but prior to' washing.

The layers can be later reconverted into stripping layers which are readily strippable in water by treating the lm element in an aqueous treating bath containing an anionic surface active wetting agent and having a pI-I of about 1.0 to 4.5. `Y1

In the preferred aspect of the invention, a stripping iilm containing two light-sensitive silver halide gelatin emulsion layers which are separated by a cold water-soluble stripping layer predominating in a sodium o-sulfobenzaldehyde acetal of a hydroxyl polymer containing a plurality of recurring l *Clif-CEDH groups as polymer forming units is insolubilized b y means of an aluminum chloride aqueous solution and resolubilized just before it is desired to effect stripping by means of an aqueous solution vof a sodium salt of an alkyl sulfate of 8 to 18 carbon atoms or a mixture of such salts.

When the insolubilization has been carried out to an excessive `degree by aging of the nlm or 'by an excess'of the aforedescribed insolubilizing metal hardening agent, it is advisable to add polyvalent metal ion sequestering agents to the aqueous solution of the anionic wetting agent.

Suitable sequestering agents include a-hydroxy laliphatic carboxylic acids, e. g., glycolic, lactic,

citric, andV tartaric; oxalicacids and Water- Vsoluble salts thereof, e. g., sodium, potassium, etc.

The invention will be further illustrated but is not intended to be limited by the following examples EXAMPLE I l A- cellulose nitrate lm base having a. thin gelatin coating Vwas coated to a weight of 52 mg. AgBr per sq. dec. vwith a gelatine-silver iodobromide emulsion which had admixed therewith 50% by weight based on the silver salt of yellow colloidal silver. A mixture of 100 parts of 100% 'hydrolyzed polyvinyl acetate (medium Viscosity- -molecular weight 15,000 to 20,000), 1,080 parts ethylene glycol, 7 3 parts of sodium-o-sulfobenzaldehyde monohydrate, and 9 parts 100% phosphoric acid-is stirred at 80 C. for 1 hour and then precipitated with 10,000 parts acetone and dried to give 142 parts of a white solid. A solution containing 50 grams of this acetal per 1,000 grams of a 10% ethanol, 90% water solution was digested 45 minutes at 125 F., cooled to 90 F.,

2,2'cyanine iodide as an ortho-sensitizing dye `was coated on the acetal layer to a weight of 48 mg. AgBr per sq. dec. This lm element con- It may be A Vsimilar film base was coated with thin gelatin substratum and dried. A gelatine-silver It constitutes the rear lm of a bipack and may be slit and perforated in like manner to form famotion picture nlm.

K Citric acid lowing ingredients:

Water (125 F. or 52 C.)' L ce 500.0

Add cold water to make 1.0 liter.

(2) Fixed 5 minutes at 68 F. in xer mixed as follows:

Water (125 F. or 52 C.) cc 750.0 Sodium thiosulfate (Hypo) g 240.0 Potassium metabisuliite g-- 24.0

Add cold water to make 1.0 liter.

(3) Treated 5 minutes at 68 F. in a bath mixed as follows:

Water (125 F. or 52 C.) Q ccr150.0 Sodium sulfate, desiccated g 50.0

VAluminum chloride, 32. B. solution cc 50.0

Borax, granular g 10.0

Add cold water to make 1.0 liter.

whereby the polyvinyl acetal became insolubilized.

(4) Washed 5 minutes in cold running water.

(5) Dried quickly in Warm air dryer.` l

The above-processed film was perfectly normal in all respects. except that the contrast appeared high due to .the presence of two image layers. Without the above insolubilization treatment (3), the stripping layer was quite soluble and dissolved in the wash water producing a badly blist'ered and poorly attached outer emulsion layer.

The outer image bearing layer of element (A) can be transferred to a separate perforated motion picture support consisting of a, transparent film base coated with a thingelatin layer. This light-insensitive lm Vwill be hereinafter referred to as a gel-blank.v y'Ihe gelatin layer is preferably coated fromva 4 to 10% .aqueous gelatin solution containing saponin and a small amount, for example, 10 to 25 cc. of 80%' lactic acid per liter. The transfer canbe effected-in the following manner: The dried element (A) is soaked in a 10% aqueous solution of sodium dodecyl sulfate buffered to a pH of 1.0 to 4.5 for 3 to 5 minutes at 68 to 72 F., pressed into registered vcontact with the acid gel-blank for about 2 minutes and then the gel-blank with the adhering outer image-bearing layer of lm (A) 4is. stripped from the remaining or lower imagebearing layer. The transferred image-bearing layer had excellent anchorage to the gelatinblank film. u

EXAMPLE II ample .I was exposed to an object field and then developed, fixed, treated, washed and` dried in the same iive steps referred to in such example. The dried iilm was soaked with mild agitation for seconds in a transferbath"havingjapH of about 3.0 and made up bywrnixi'ng th`"fo1 @Grams Sodium dodecyl'sulfate, dry r r ,-v 50 Monohydrogen y disodium phosphate: 12H29- .15

Water to make 1 liter.

(2) The outer layer of the Wet iilm wasthen rolled into Contact with the gelatin surfaceeof an acid gel-blank of. the 'itype described in Example I., The resulting film was stripped in jliliefmanner; @The jgel'blan-k had excel-lent- -adherence to- `the "transferred outerimage-bearing layer' 'from' lthe ,lm' (A). "The presence of- Acitric acid" in;l the stripping; solution markedly reduced the time :necessary to *produce stripping. 1Note in Example I, 3 yto f5- minuteso soaking was required.

EXAMPLE III Stripping films; similar Ato that; described in Example: I' were' exposedA to an object field and then 'developed'.ixedf, treated; washed nand treated by the same' fivev'procedures ofsuclr example;

sample ,vivassoaked for-L32 minutes-'with agitation1in-Waterand the Iouteriayerawas rolled ccI-Itactwith `tlfrfee gelatin layero fan 'acid gelatin-biank'hhn of the type -eisciosedlir-i ample I.

"fjA 4second sample Was'soakedior Zfminutes in an e'iqueous`v solution 4contain-ing -10 gra-ms lof sodium-dodecylsulfate |100-k cc. of water and then-j for' -1- minute solution made by adding "101-4g-ramsi ofsodi-um*idodeeylsulate; 60` cc.- -of '-95% ethanol and '2 ce. off-glacial acetic acid to va -su'ieientameunt of water tomake -10'0=cc. of solution. The-film -wasagitated duringthe soaking `per-iodlanislthen :rolled -in-to contact With-an acid gel-blank and later's'tripped after the :man- Lner-vdescriloediin-Exam-ple I.

V-Ai third sample of *.lthe'dried. film Was treated 1inI thesamefrriamierN asy theY second.v sample except vathat 110 grams. ofv sodiumvdodecyl sulfate in each solution-Were replaced loy 1'33 vcc. of ya "30% aqueoussolutionof sodium octyl'sulfate. 1 Aftourlth samplevof the. dried.` i-lmnwasarea-ted '2in-the same Way as` lthe.-second vsample .except that Mgr-ams :of sodium Ldodecy-l..sulfatel in Aeach `r seliitio'n were-replaced by -20 grams- -of :aPmiXture of higher primary.-fandrsecondary afl-kane-sultonic `:acids :predominatingA 11a-secondary alkanef sulonic acidsfofrlto'lfcarbori-atomsa QA :fith samplesof thedried:iilm element was ttreatedin the same marmer asithe secondrsarrrple except 4)tl-iat the 10' grams 'of' sodiumv .dodecyl sulfate were replaced by 10 grams lof. a mixture ieii'sodiurn` :alkane ,sulfonates of* .8! toy H10' `carbon eetoms.

mier-h sample cfa-the- =uriedfrriim das. treated fithe- .fsame way. as .the fsecondgsample. except :that Ythe 310 .gramslof-:sodiumdodecyl sulfate were .replaced by L10; gramsJoi/f:sodium tetra-lin sulluonate. lheouter layer .of the-'2nd, :3rd, `Ath, li5t-h,A and: 6th :samples after transfer to y.the.gelatin- .hlankfflm wereAV readily.l stripped. zfr'om .the Aremanning; .imageebearinglayer of the .front :ulm due; to the :resolubilizing:character .ofrthe baths. There was no perceptible resolubilizingrinpthe first-:bath `:and stripping transfer lco1ild=.not be -eiectivelyscarried ,-zo.ut.v .'l'hexanchorageinl the V2nd, -.3rd, 1and:v 6th :samplesf was aespeciallyigcod.

A; photographic ,stripping-.nlm similar-tofthat pffflilxample was*processedasidllowst ;.(lg) Developedgrfor 15 minutes zatz'? E:;inz.the 1-developeli-of;fllxample.1. Y

image-bearing layle'rvto faseparate .gelatinblank` iilm. The potassium alum inl the xigfbath insolubilized-the stripping layer land -prewented .detachment -off 'the` Jupperlax'f'er during Washing.

,Thelstrippi-nglayenwas resolubilized =by the bath described in ExamplefI.' *Therewas good-adherencebetweenetheoutengelatin l' layer andthe gelede layer ofthe rg@latin ma-ak aim, and the transf-erred Jla-yer-was *readily strippedffrom the lower layer; Somewhat more-rapid-reselubilizu tion was attained witha `bath containing-path -the anionic wettingv agent-and citric ialdrinfthe amount of 15 grams 'perf-liter.

A 'iilmsimilar to that'. QIjEXamplel wasmacessed asfollows:

. .(1) Developed" for' 1'5` minutes; Lat. 68T" F'.' in same developer'as Example f1.5

(2) Fixed ior 15. minutes.' at' efr?I F. giniharden ing xer of following composition:

Potassium alum g 10.0 Cold Water added to makelliter.

(3) Washed 5 minutes in cold running Water. "(4). 'Driedquickly n I' c '(15) '-Dried'iil-m'- transferred -after'lthellmafnner 'The follovfing example iillustrates'theuse of insolubilizing or hardening agents for thef-so'- dium-osulfobenzaldehxder,. acetal stripping layer primto coating. It eliminates an insolubilizing @treatmentdurinaprocessine; e- .g', after'singi.

A cellulose lnitrate lm;...base gelatin-coating:Wasicoated toa` weightiolxz'mg. AgBr per sq. dec. with a gelatino-silver iodobromide emulsion which had admixed therewith -Y5U%-by Weight based on the silver salt of yellow colloidal-silver.. A mixture of' 10U-parts of f100`-% v hydrolyzed Apolyvinyl acetate (medium =Viscosity-- Vmolecular Weight 15,000-A to :20,000JFy 11,080'fiparts ethylene glycol, 73 partsosodium-oisulfobenzaldehyde -monoh-ydrate, andi-9, parts 100%.' phosphoric acid fis stirred at 809 ,0..for ihourandthen precipitated with k1001,-000par-ts acetonelandadred .to-gine lll-2, parts fof.V a kWhite* Solid. solutiony `.ccntaining,v2do grams- `Aof this. Aacetal 'in 145000 grams of l10%sethanolwas dgestedzmnlltes .at 12,5?7 iandgcooled.to 90 F.

09003; inch;V :as ai control mithnnaffutther additions.' Ilogthe .remaining pcrticns ,theiint- .cation ameuntswof 10.1%aqueouschrome alum solution were added: t

Portion:

Cubic centimeters 'gi phosphoric acid -4 ,witncistmeunwater'miu saving a pH of'abopt 1.'7. l

and 'samples' of the above lm were coated on the emulsion side with these solutions in layers 0.0001 to 0.0003 inch thick. i l

-A1l ofthe samples were then coated with gelatine-silver iodobromide emulsion containing 1,1-methyl-2,2.-cyanine iodide to a weight of 48 mg. AgBr per sq.,dec. -f

These film elements were processes as described in Example I, stepsy (l) to (5) except that step (3) was omitted. During theY washing step the stripping layeraof the control nlm (A) softened, allowing the ortho emulsion layer to blister and become detached from the lower emulsion layer. Films made from portions B, C, and D, however, all exhibited firm attachment during all processing steps. f,

However, when they were bathed in a solution of the following composition Grams Sodium dodecyl sulfate (dry) 25.0 Sodium tetralin sulfonate 25.0 Monosodium dihydrogen phosphate monchydrate 5.0 Citric acid (U. S. P.) 16.0 Water to make 1.0 liter.

Phosphoric acid 85% to lower pH to 2.0.

the stripping layers dissolved readily and permitted the ortho emulsion layers to be detached. The resulting front film element wasprocessed and stripped, as described in Example I, except lthat step (3) was eliminated with similar results.

EXAMPLE VII The process of Example II was thrice repeated by substituting for the transferjbath of such example one of the following baths A and B and a third bath made by mixing 500 cc. of the two baths. l'

85% phosphoric acid added to lower pH to 2.0.

Bath B was found to be faster acting than A requiring only 45 seconds to soften the film preparatory to rolling in contact with the acid gellblank. However, the anchorage to the gel-blan was somewhat less than with Bath A.

The mixed bath was rapid-acting and had excellent anchorage characteristics.

EXAMPLE vnr Samples of a illm element of the type disclosed in Example I were processed by each of the've lsteps described in that example, soaked for 20 to 30 :seconds in the following transfer solutions at 70 F. and then rolled 'in contactwith an acid gel-blank after the manner 'set fforth in Vthat example.

" Bath-1 v cc.` 85%3 diluted to 260 cc.

. Bath-2 Bath-3 Phosphoric acid 4 cc. 85% plus 35 cc. of a 30% aqueous mixture of sodium alkane sulfonates of 8 to 10 carbon atoms and distilled water to 250 cc.. said solution having a, pH of 1.7.

4Bath-1 produced poor anchorage of the transferred image-bearing layer to the gelatinblank lm. Bath-2 had anchorage greatly superior to Bath-1 while Bath-3 was intermediate in properties. y

In place of the anionic wetting agents described-1n the above examples, there may be substituted a large number of other speciiic wetting agents of this type. Suitable agents include the sodium potassium and ammonium salts of decyl, dodecyl, tetradecyl, hexadecyl, octadecyl and cleyl sulfate; the triethanolamine, triethylamine, cyclohexylamine, piperidine, and tetraethylammonium salts of such sulfates; and mixtures of any two or more of such salts. A good commercial mixture is composed of the sodium salts obtained by sulfating the mixture of alcohols obtained by the hydrogenation of coconut oil. Sodium potassium and ammonium isopropyl naphthalene sulfonates are also useful.

The sodium dodecyl sulfate used in the foregoing examples was electrolyte free but contained minor amounts of other sodium n-alkyl sulfates of 10 to 18 carbon atoms being made by sulfating a fraction of the higher alcohols obtained from coconut oil as described above.

The pH of the transfer solutions can readily be regulated by the addition of buffering agents. In addition to those of the examples there may be used potassium acid phthalate, potassium acid Vtartrate, sodium citrate, sodium tartrate, and

sodium lactate.

Similarly, in place of the specific sequestering agents which are referred to above, there may be substituted similar amounts of other agents of this type. Among such additional ag-ents which can be used in place of, or in admixture with, the a-hydroxy aliphatic carboxylic acids, e. g., lactic, citric, tartaric, or oxalic acids are sodium hexametaphosphate, glycerine, ethylene glycol, urea, sorbitol, thiosorbitol, and 5% aqueous sucrose. The latter materials, however, are rather weak sequestering agentsfor metal ions, e.'g., aluminum.

In place of the specic lm elements described in Example I, there may be substituted various other film elements having similar polyvinyl acetal sulfonic acid or carboxylic acid compound stripping layers. Among such acetals are those describedin German Patent 643,650 and U. S. Patent 2,310,943. The free acids of such acetals can be converted into water-soluble salt groups by a. simple neutralization. To be more specific, they can be neutralized or made slightly basic (pH 79) by salt formation with alkali metals, ammonia, or amines which form water-soluble salts, e. g., mono, di-, and tri-methylamine, mono-, di-, and tri-ethylamine, piperidine. cyclo- ,hexylamina ethylenediamine-1,2, hexamethylenediamine1,6, piperazine, vmorpholine, etc. Neutral or slightly basic` (pH 8 9) solutions or cohol of high rmole argot' aureo Between ro lffm-1135 7a jf i tpe' hdroiifl" gr'p aire" akitalized` with"v tl" ldeiv hydes. The total acetal. content" le'c' on these gures will vary depending-on the hydroxyl content of the polymer, bt it has been found that the best resultsere 'obtained ywhen between- 5I amdE 17% of theo-carbonatoms oi-.tl'iev polymerY chain' -SOze radical'.- The a'oe'tals havn'gfthis' degree v and eit-thembefore stripping;A

'stripping operation in a different room fro 1n which the chemical xphotographic: processing, el g developing and liking', t

me that; eguf' stripping. A further advantageritl't :i: pmg operations can'ge carried out at a, centra loboratory while pro'dution o'mpanies on loca.- tiorrcanprocess alnolview? each daayfs` f Silver halide-emulsionlayerswhich are ser:aratetr:.y

Mila Q t salt-'forming cation, which aldehyde is otherwise unsubstituted, fixing said element, treatingsaid element in an aqueous 4solution containing a water-soluble. inorganic polyvalent,` metal gelatinhardening agentjwhich. yields metal ions having a Valence of 3 to 4 to reducethe Watersolubility ofthe acetal layer, washing the resulting element and drying the same, subsequently resolubilizing said layer by treating it in an aqueous bath having a pH of about 2.0 to 3.0 containing an anionio surface. active wetting agent, pressing the outer image-bearing layer of said element into contact with a lm bearing a gelatin layer and stripping thefiinage-.bearing layer 'adhering to said gelatin layer from the 'Aremainder'of said. exposed photographic film;

"2J The process which comprises developing an exposed photographic lm element having superposedv thereon two latent image-bearing gelatino silverhalide emulsion layers which are separatedV by" a stripping layerV consisting essentially of a water-solublev macromolecular acetal of a hy-l droxyl Apolymer having a plurality of recurring intralinear CH2-on oH` groups with an aldehyde containing a solubilizing group taken from the class consisting of -COOZ and -SOsZ'where Z is a member taken from the group consisting of hydrogen and a water-soluble salt-forming cation, which aldehyde is otherwise 5.The process which comprises developing an exposed photographic film element having superposed therein two latent image-bearing ge-i latino silver halide-emulsion layers which are` separated by a stripping layer consisting essentially of a water-soluble sodium-o-sulfobenzaldehydeacetal of polyvinyl alcohol, fixing said element, treating said element in an aqueous solution containing a water-soluble inorganic poly.-

valent lmetal gelatin-hardening agentv which yields metal ions having a valence of `3 to tto reduce the water solubility of thejacetal layer,

washing the resultinggelement and drying the same,r subsequently resolubilizing said layerby treating it in an aqueous bath having a pH of about 1.0 to 4.5 containing an anionic surface active wetting-agent, pressing the outer image-K,

bearing layer of said element into contact with a iilmjmbearing a gelatinlayer and strippingv the image-bearing layer adhering to said gelatin,-

` separated by a stripping layer consisting essenunsubstituted, xing said element, treating said g element in an aqueoussolution containing aluminmchloride, washingthe resulting element and dryhgthe same, subsequently resolubilizing said layerby treating it in an aqueous bath having a pI -I of about2.0 to 3.0 containing an anionic surface active wetting agent, pressing the outer image-bearing layer of said element into contact with` a lm bearing a gelatin layer and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic film.

`3. The process which comprises developing an exposed photographic iilm element having superposed thereon twolatent image-bearing ge-` latino silver halide emulsion layers which are separated by a stripping layer consisting essentially .of 'a water-soluble macromolecular acetal of ahydroxyl polymer having'a plurality of recurring intralinear i CH2-orion groupswith an aldehyde containing a solubilizing group taken from the class consisting of COOZ and -SOaZ where Z is a member taken frozn the group consisting of hydrogen and a water-soluble salt-forming cation, which aldehydeis otherwise unsubstituted, iixing lsaid ele-4v ment, treating said element in an aqueous solution containing aluminum chloride, washing vthe resulting element and drying the same', subsequently resolubilizing said layer by treating it iu an aqueous bath having a pH'of about 1.0 to 4.5 containing an anionic surface active wetting agent and an aluminum ion sequestering aliphatic rcarboxylic acid, pressing the outer imagebearing layer of said element into contact with a film bearing a gelatin layer and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic nlm.

4. 'A process as set forth in claim 3 wherein said wetting agent is sodium dodecyl sulfate and said sequestering acid is lactic acid,

tially of a water-soluble sodium-o-sulfobenzaldehyde acetal of polyvinyl alcohol, iixing said element, treating .said element in Van aqueous solu-` tion containing aluminum chloride, washing the resulting element and drying the same, subscgquently resolubilizing said layer by treating it in Y.

anlaqueous bath havinga pH of about 1.0 to 4,5 containing an anionic surface active wetting agent, pressing the outer image-bearing layer of said element into contact with a lm bearing-a gelatin layer and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic film,

7. A process as set forth in claim 5 whereintheV gelatin layer of the second film contains an acid.

8. The process which comprises developing an,vv

exposed photographic film element having Superposed thereon two latent image-bearing gelatino silver halide Lemulsion layers which areI separated by a stripping layer consisting essentially of a waterrsoluble macromolecular acetal of a' hydroxyl polymer having a plurality of `recurring intralinear -CHFLLHOH groups with an aldehyde containing a solubilizing group taken from the class consisting of Y -COOZ and -SOsZ where Z is a member takenV .Y

from thegroup consisting of hydrogen and a water-.soluble salt-forming cation, which aldehyde is otherwise unsubstituted, fixing said element, treating said element in an aqueous solution containing aluminumA chloride, washing the resulting element and drying the same, subse-V quently resolubilizing said layer by treating it 1n anaqueous bath having a pH ofabout 1.0 to 4.5 containing an anionic surface active wetting agent and an aluminum ion sequesterng aliphatic carboxylic acid, pressing the outer imagebearing layer of said element into contact with a,

lm bearing. a layer of gelatin containingvan acid and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic film.

exposed photographic iilm element by a stripping layer consisting essentially of a water-soluble macromolecular acetal of a hydroxyl polymer having a plurality cf recurring intralinear i -CHz-CHOH groups with an aldehyde containing a solubilizing group taken from the class consisting of -COOZ and -SOQZ where Z is a member taken from the group consisting of hydrogen and a water-soluble salft-forming cation, which aldehyde is otherwise unsubstituted, fixing said element, treating said element in an aqueous solution containing aluminum chloride, washing the resulting element and drying the same, subsequently resolubilizing said layer by treating it in an aqueous bath having a pI-I of about 1.0 to 4.5 containing a sodium dodecyl sulfate and an aluminum ion sequestering aliphatic carboxylic acid, pressing the outer image-bearing layer of said element into contact with a lm bearing a layer of gelatin containing an acid and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic lm.

10. 'I'he process which comprises developing an exposed photographic film element having superposed thereon two latent image-bearing gelatine silver halide emulsion layers which are separated by a stripping layer consisting essentially of a water-soluble macromolecular acetal of a hydroxyl polymer having a plurality of recurring intralinear groups with an aldehyde containing a solubilizing group taken from the class consisting of -COOZ and -SOaZ where Z is a member taken from the group consisting of hydrogen and a Water-soluble salt-forming cation, which aldehyde is otherwise unsubstituted, xing said element, treating said element in an aqueous solution containing aluminum chloride, washing the resulting element and drying the same, subsequently resolubilizing said layer by treating it in an aqueous bath having a pH of about 1.0 to 4.5 containing an anionic surface active wetting agent and an aluminum ion sequestering agent, pressing the outer image-bearing layer of said element into contact with a lm bearing a gelatin layer and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic film.

11. The process which comprises developing an exposed photographic film element having superposed thereon two latent image-bearing gelatine silver halide emulsion layers which are separated by a stripping layer consisting essentially of a water-soluble macromolecular acetal of a hydroxyl polymer having a plurality of recurring intralinear 4in1-Hon y' groups with an aldehyde containing a solubiliz- 14 ing group taken from the class consisting of `COOZ and -SO3Z where Z is a member taken from the group consisting of hydrogen and a water-soluble salt-forming cation, which aldehyde is otherwise unsubstituted, xing said element, and washing the element, characterized in that after the developing step and prior to the washing step the developed element is treated in an aqueous solution containing a water-soluble inorganic polyvalent metal gelatin-hardening agent which yields metal ions having a valence of 3 to 4 to reduce the water solubility of the acetal layer, drying the washed element subsequently resolubilizing said layer by treating it in an aqueous bath having a pH of about 2.0 to 3.0 containing an anionic surface active wetting agent, pressing the outer image-bearing layer of said element into contact with a iilm bearing a gelatin layer and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic lm.

12. The process which comprisesdeveloping an exposed photographic lm element having superposed thereon two latent image-bearing gelatine silver halide emulsion layers which are separated by a stripping layer consisting essentially of a water-soluble macromolecular acetal of a hydroxyl polymer having a plurality of recurring intra-linear -cHz-CIJHOH groups with an aldehyde containing a solubilizing group taken from the class consisting of -COOZ and -SOaZ where Z is a member taken from the group consisting of hydrogen and a water-soluble salt-forming cation, which aldehyde is otherwise unsubstituted, fixing said element in an aqueous solution containing a watersoluble inorganic polyvalent metal gelatin-hardening agent which yields metal ions having a valence of 3 to 4 to reduce the water solubility of the acetal layer, Washing the resulting element and drying the same, subsequently resolubilizing said layer by treating it in an aqueous bath having a pH of about 2.0 to 3.0 containing an anionic surface active wetting agent, pressing the outer image-bearing layer of said element into contact with a lm bearing a gelatin layer and stripping the image-bearing layer adhering to said gelatin layer from the remainder of said exposed photographic film.

JACOB QUENTIN UMBERGER. ARTHUR WILLIAM GRUMBINE.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 2,328,034 Sease et al. c Aug. 31, 1943 2,350,380 White f June 6, 1944 2,397,452 White Mar. 26, 1946 2,462,503 Jennings f Feb. 22, 1949 

11. THE PROCESS WHICH COMPRISES DEVELOPING AN EXPOSED PHOTOGRAPHIC FILM ELEMENT HAVING SUPERPOSED THEREON TWO TALENT IMAGE-BEARING GELATINO SILVER HALIDE EMULSION LAYERS WHICH ARE SEPARATED BY A STRIPPING LAYER CONSISTING ESSENTIALLY OF A WATER-SOLUBLE MACROMOLECULAR ACETAL OF A HYDROXYL POLYMER HAVING A PLURALITY OF RECURRING INTRALINEAR 